For purposes of possible transplantation to a recipient eye, the cornea from a donor eye is typically excised in a generally circular section of cornea tissue which is typically subjected to a variety of physical manipulations including a trephining procedure in which a circular corneal button of the desired size is cut out from the corneal tissue for use as a transplant.
It is well known that basic trephining procedures involve the use of cutting blocks and disposable cutting elements in what is commonly known as the "cookie cutter" technique. The cornea tissue is carefully placed epithelial-side down on a block made out of hard inner material such as Teflon, such that the center of the cornea tissue is aligned with the center of the indentation, and the cornea tissue rests in approximately its normal curvature during trephining. A circular metal trephine blade is then carefully aligned and oriented to as to hover above or lightly touch the cornea tissue at the desired, generally central location. The blade is then tapped or turned down into the cornea tissue with sufficient force and to a sufficient distance to cut out a corneal button against the cutting block. Examples of these trephining arrangements are disclosed in U.S. Pat. No. 4,718,420 issued Jan. 12, 1988 to Lemp, U.S. Pat. No. 5,011,498 issued Apr. 30, 1981 to Krumeich et al, U.S. Pat. No. 5,019,084 issued May 28, 1991 to Aysta et al and U.S. Pat. No. 5,092,874 issued Mar. 3, 1992 to Rogers.
These arrangements employing the cookie cutter technique all share a serious drawback in that the inherent cutting action takes place when the trephine blade passes through the cornea material and then hits the Teflon block underneath it causing the sides of the corneal button to be wavy and uneven with major destruction to the endothelial cells. The condition and appearance of the endothelial and epithelial surfaces are critical factors to be determined in deciding whether a particular corneal tissue is suitable for implantation. Abrasions and loss of cells from the endothelial surface are major factors for rejecting many corneal tissues for use and can be attributed at least in part to damage done to the tissue during trephining. An additional problem using the cookie cutter technique occurs when the trephine blade contacts the Teflon block at which time the trephine blade is considered disposable. This means that the trephine blade must be replaced after each cutting operation, which is an unnecessarily costly expense.
Accordingly, it remains desirable to provide an apparatus and method for supporting and cutting a cornea tissue which effectively avoids the disparities and distortions present in prior art devices. It is further desirable to provide a system which provides a centralized cut of corneal button, a reduction in endothelial cell damage, a reusable trephine blade, and a safer handling of the corneal tissue.